Suction valve of air and gas compressors



Nov. 16 1926. 1,607,418

E. PRESTAGE SUCTION VALVE OF AIR AND GAS COMPRESSORS Filed July 2'7, 1926 I [nuenlbr I Prifge 2? W .lz lzorneyx Patented Nov. 16, 192-6.

UNITED STATES PATENT OFFICE.

EDWIN PRESTAGE, OF LONDON, ENGLAND.

SUCTION VALVE OF AIR AND GAS COMPRESSORS.

Application filed July 27, 1926, Serial No. 125,286, and in Great Britain June 18, 1825.

My invention relates to improvements in the mechanism adapted to operate the suction or inlet valves of air and gas compressors and more particularly those compressors for compressing ammonia and carbonic acid gas for refrigerating purposes.

A number of compressors now in use for this purpose have what is known as trunk pistons working in a cylinder said pistons being fitted with valves of the plate or mushroom type operated more or less mechanically by their own inertia and the reciprocating action of the piston. The action of these valves may approximate to their being open when the piston is at the top and closed when it is at the bottom of its stroke, provided the piston speed is comparatively slow, but when higher piston speeds are employed it is well known that a considerable amount of gas-slip results.

Since in compressors of this type the top of the piston with its valve practically touches the cylinder cover or head carrying discharge valves, it is essential that the valve should not commence to open until the piston has moved down slightly as otherwise damage to the valve or lifting mechanism would result. Another reason for opening the valve a little late is to provide for the re-expansion of any gas left at high pressure in discharge valve pockets, etc. 7

The present invention is more particularly designed to provide a simple method by which the gas inlet valve can be opened at any reasonable point around the top dead centre, either before or after and to close said valve at any reasonable point around the bottom dead centre either before or after.

According to my invention distance pieces are fixed on the top end of the connecting rod and a roller is adapted to travel between said pieces whereby the mushroom valve fitted into the trunk piston is opened or closed by the oscillations of the connecting rod at predetermined points during the stroke of the piston. A rocking arm is positioned between the. roller and the lower end of the valve stem to positively lift the latter as hereinafter described.

Referring now to the accompanying drawing in the trunk piston a is arranged a mushroom valve 6 held down by a spiral spring 0 and adapted to be lifted by the rocking arm (Z at the moment when the connecting. rod 6 brings the roller f underneath the projection of the rocking arm d. A lug h on the top of the connecting rod 6 forces the roller f to travel a distance which will be in accordance with the stroke of the crank and the obliquity of the connecting rod.

It will be seen that according to the relative positions of the roller 7 and the projection 9 of the rocking arm d the valve can be made to open either early or late with reference to the piston towards the top of its stroke. hen the crank pin is approximately half way down the stroke and the top of the connecting rod commences to return, it will be seen that the other lug k on the top of the connecting rod 0 is at a short predetermined distance from the roller f. The roller 7 being then wedged between the top of connecting rod 6 and the projection g of the rocking arm (Z commences to roll and continues to do so until the face of the lug k catches it up and completes the movement which allows the valve to close. 7

It will be easily seen, therefore, that when the top of the connecting rod 6 is moving in the direction of the arrow A, the roller is being positively forced over all the way, but when the top of connecting rod 6 commences to move in the direction of the arrow B, there is a delayed action due to the distance which the roller is allowed to roll backward across the top of the connecting .rod which delays the closing of the valve and so obtains the advantage of filling the cylinder with the maximum gas pressure before the piston commences its upward stroke.

lVhat I claim is 1. In an .air or gas compressor in combination, a cylinder, a trunk piston working in said cylinder and provided with a mushroom valve, a connecting rod, distance pieces fixed on the top end thereof and a roller adapted to travel between said pieces whereby the said mushroom valve is opened or closed by the oscillations of the connecting red at predetermined points during the stroke of the piston.

2. In an air or gas compressor in combination, a cylinder, a trunk piston working in said cylinder and provided with a mushroom valve, a connecting rod, distance pieces fixed on the top end thereof, a roller adapted loo to travel between said pieces and a rocking arm positioned between said roller and said mushroom valve.

3. In an air or gas compressor 1n combination, a cylinder, a trunk piston Working end thereof, a roller adapted to travel between said pieces, a rocking arm positioned between said roller and the lower end of said valve stem and a projection on said rocking arm.

In testimony whereof I affix my signature.

EDWIN PRESTAGE. 

